Platforms and structures which are used for offshore work in varying depths of water find utility for a number of purposes. Often such platforms are utilized to support equipment and like material for drilling offshore wells to produce gas and/or crude oil.
Because the platforms are so expensive, particularly for use in deep water, they are often used as gathering centers for a plurality of remote or dispersed wells in addition to on-platform wells. Thus, while a particular offshore reservoir might embody any number of producing wells, the production flow from the remote wells can be carried through subsea pipelines to a single desired gathering point.
Platforms or structures of the type presently contemplated are utilized to gather the crude product, whether it be gas or oil, into a central treating area. From there it can be transshipped by way of vessels or other means, or merely pumped to a central station onshore for further processing.
Since the product carrying pipelines are disposed at the ocean floor, it is necessary that they be led from the remote well head to the foot of the offshore structure. From there the pipeline is connected to a suitable extension of the pipeline or riser so that the product can be either pumped or forced by its own pressure upwardly through the riser to the deck of the platform.
Platforms of this type are normally provided with a working deck which is supported above the water's surface by at least one, and preferably by a number of heavy support legs. The latter serve not only to position the platform firmly at the offshore site but also provide support and protection to the plurality of on-platform well conductors and the risers which normally extend from one or more pipelines up to the deck.
During the fabricating step of an offshore platform, normally the required complement of well conductor guides and risers are preplaced within the structure so that they are an integral part thereof when the platform is installed at the offshore site. However, often the number of risers which are initially built into the structure is insufficient to accommodate the number of remote or dispersed wells that have later been discovered and found to be productive. It therefore may become necessary at a future date to install additional risers for pipelines to be gathered into the foot of the structure.
When adding risers not previously planned for, it is necessary to safeguard them against damage which might be caused by water forces or floating objects such as debris, ice and the like. It is also necessary to minimize the weight and size of the added risers and their attachments and supports.
In such an instance, the riser can be made as a heavy walled self-protective member. However, this would not minimize weight and size. It is considered more practical to pass one or more risers directly through an existing or added vertical protective member. In platforms with on-platform wells, guides are preinstalled in the structure during fabrication to protect and stabilize the on-platform well conductors. Usually, extra conductor slots are provided beyond the minimum required.
In platforms where an extra conductor slot or slots are available and additional pipeline risers are required, the addition of the protective vertical member into the existing unused conductor slot and guides will be most practical. If no conductor slots remain unused, the addition of the protective vertical member with necessary supports may be accomplished in a manner somewhat similar to the on-platform well conductors.
In the presently disclosed arrangement, there is disclosed an addition to an offshore structure or platform of the type contemplated. The addition being that, an upright protective member is provided which is vertically and horizontally self-supporting and permitting insertion of a number of fluid carrying risers therethrough as needed. If placed in an existing well conductor slot, no modifications to the platform structure are required and no increase in original design loadings or weight added to the deck is created.
The upright member is thus provided with upper and lower spaced apart segments which are connected by an intermediate connecting element disposed therebetween. Said upright member extends to and into the ocean floor. It is, most essentially, capable of permitting a number of risers to be lowered therethrough and which are deflected outwardly in a desired direction or directions. Further, it protects the risers and supports the riser weight.
It is therefore an object of the invention to provide a modification to an offshore structure by the provision of a unique riser support structure. A further object is to provide a structure of the type contemplated that is initially fabricated in a manner to be readily adapted in the future by the addition of further fluid carrying risers after the unit has been installed at an offshore site. A still further object is to provide an offshore structure that is provided with means to receive fluid carrying risers longitudinally therethrough in a manner that the risers will be bent or deflected away from their normal downward course during installation.